SERVER DEVICE, CONCEALED SEARCH PROGRAM, RECORDING MEDIUM, AND CONCEALED SEARCH SYSTEM

摘要

A server device 201 comprises a communication part 231, a search history storage region 213, a data storage part 210, and a checking part 220. The communication part receives a set of a trapdoor and a deterministic encrypted keyword from a search device 401. The search history storage region 213 stores the set of the trapdoor and the deterministic encrypted keyword. The data storage part 210 stores keyword information in which search target data and an encrypted keyword are associated with each other. If the deterministic encrypted keyword is obvious, a deterministic encrypted keyword corresponding to the encrypted keyword is additionally associated with the search target data and the encrypted keyword in the keyword information. The checking part 220 checks whether or not a deterministic encrypted keyword which matches the received deterministic encrypted keyword exists in the search history storage region 213. If the deterministic encrypted keyword exists, the checking part 220 executes a concealed search targeting the data storage part 210, based on a deterministic encryption scheme using the deterministic encrypted keyword existing in the search history storage region 213. If the deterministic encrypted keyword does not exist, the checking part 220 executes the concealed search targeting the data storage part 210, based on a probabilistic encryption scheme using the received trapdoor and the encrypted keyword stored in the data storage part 210.

主权项

1. A server device that executes a concealed search, comprising:
a server-side communication circuit that receives a set of a trapdoor and a deterministic encrypted keyword, as a concealed search request from a search device, the trapdoor being generated from a keyword in accordance with a probabilistic encryption scheme and used for a matching check with an encrypted keyword obtained by encrypting a keyword of search target data in the concealed search in accordance with the probabilistic encryption scheme, the deterministic encrypted keyword being generated from the keyword from which the trapdoor has been generated, in accordance with a deterministic encryption scheme; a search history storage circuit that stores the set of the trapdoor and the deterministic encrypted keyword, as a history of a past concealed search request, the set being received by the server-side communication circuit; a data storage circuit that stores keyword information in which the search target data and the encrypted keyword of the search target data are associated with each other, wherein if the deterministic encrypted keyword is obvious, the deterministic encrypted keyword corresponding to the encrypted keyword is further associated with the search target data and the encrypted keyword of the search target data in the keyword information; and a checking circuit that checks whether or not the deterministic encrypted keyword which matches the deterministic encrypted keyword received by the server-side communication circuit exists in the search history storage circuit; and if it is decided that the deterministic encrypted keyword exists, executes the concealed search of the search target data targeting the data storage circuit, based on the deterministic encryption scheme using the deterministic encrypted keyword existing in the search history storage circuit, and if it is decided that the deterministic encrypted keyword does not exist, executes the concealed search of the search target data targeting the data storage circuit, based on the probabilistic encryption scheme using the trapdoor received and the encrypted keyword of the keyword information stored in the data storage circuit.